The present invention relates to hinge mechanisms for vehicle seats, and to seats including such mechanisms.
More particularly the invention relates to a hinge mechanism for a vehicle seat for interconnecting two elements forming parts of the seat and mounted to pivot relative to each other about a pivot axis, said hinge mechanism comprising:
first and second cheek plates for securing respectively to the two seat elements, said cheek plates being mounted to pivot relative to each other about said pivot axis, the second cheek plate being permanently secured to a set of teeth extending over at least an arc of a circle centered on the axis of rotation;
a plurality of locking slugs each provided with a set of teeth suitable for co-operating with the teeth of the second cheek plate, each locking slug being movable relative to the first cheek plate between firstly an engagement position in which the teeth of the locking slug co-operate with the teeth of the second cheek plate to lock the hinge mechanism, and secondly a retracted position in which the locking slug does not co-operate with said teeth of the second cheek plate; and
a cam mounted to pivot about the pivot axis and urged resiliently towards a rest angular position, said cam presenting a peripheral edge cut out in such a manner as to bear against the locking slugs, placing said locking slugs in their engagement position when the cam is in its rest position, and the cam being movable by a user into an actuation angular position in which said cam enables the locking slugs to move towards their retracted positions, and disengagement means adapted to place the locking slugs in their retracted positions when the cam is in its actuation position.
The above-mentioned disengagement means can be constituted, in particular, by a control plate turning with the cam and provided with camming edges that cooperate with the locking slugs. The disengagement means could optionally also be constituted by one or more springs, or possibly merely by the shape of the teeth of the second cheek plate and of the locking slugs, which shape would then be adapted to cause the slugs to slide radially inwards as soon as the two cheek plates start to turn relative to each other while the cam is in its actuation position.
Document EP-A-0 720 930 describes an example of such a hinge mechanism intended to enable the angular position of the seat back to be adjusted relative to the seat proper. That hinge mechanism has three locking slugs that are angularly distributed at 120xc2x0 relative to one another.
The hinge mechanism described in that document gives entire satisfaction, however the inventors of the present invention have set out to improve it further, so as to make it lighter in weight and less expensive, or so as to make it stronger at comparable weight and cost.
To this end, the invention provides a hinge mechanism of the kind in question that is characterized in that there are two locking slugs, and in that said locking mechanism further comprises at least two abutment zones which are fixed relative to the first cheek plate and which face substantially radially towards the central pivot axis and towards the two locking slugs respectively, the peripheral edge of the cam being shaped so as to bear radially against said abutment zones when the cam is in its rest position, the two locking slugs being placed on one side of a diametral line intersecting the pivot axis, and the two abutment zones being placed on the opposite side of said diametral line.
By means of these dispositions, a hinge mechanism is obtained which, when it includes only the two locking slugs for locking the two cheek plates relative to each other, presents braking strength comparable to prior art mechanisms having three slugs, while nevertheless being lighter in weight and less expensive since one of the slugs is omitted. The strength of the mechanism of the invention is due to the presence of the two abutment zones which take up the forces tending to move the locking slugs in reverse when a large torque is applied between the first and second cheek plates, in particular in the event of a traffic accident. In particular, because the abutment zones are disposed substantially in an open V-shape looking towards the locking slugs, the cam is in stable equilibrium and therefore does not tend to escape from said abutment zones when the hinge is subjected to a large torque.
Furthermore, the internal arrangement of the hinge mechanism of the invention releases a fraction of the inside space between the first and second cheek plates, and advantage can be made of this space to add additional functions to the hinge mechanism.
In particular, this empty space can be used for adding one of the following to the hinge mechanism:
a device for memorizing an angular position, similar to the device described in document FR-A-2 770 469 for example, so as to enable the back of a vehicle seat to be folded down in order to give access to rear seats of the vehicle, and then return the back to its initial angular position; or
a jamming device similar to that described in document FR-A-2 790 230, or indeed a jamming device of the kind described below.
In preferred embodiments of the invention, use can optionally also be made of one or more of the following dispositions:
the two abutment zones present circularly-arcuate shapes centered on the pivot axis, and the peripheral edge of the cam itself presents two circularly-arcuate portions centered on the pivot axis and coming into contact with each of the abutment zones respectively, at least when the cam is in the rest position;
said two circularly-arcuate portions of the peripheral edge of the cam have the same radius and form portions of the same circularly-arcuate sector belonging to said peripheral edge;
the two abutment zones are disposed substantially at 120xc2x0 to each other about the pivot axis, and the two locking slugs are likewise disposed at substantially 120xc2x0 to each other about the pivot axis;
the mechanism includes at least one jamming member of a shape that diverges going radially towards the teeth of the second cheek plate, and including a set of teeth facing said teeth of the second cheek plate, said jamming member being mounted on the first cheek plate in such a manner that its teeth come into engagement with the teeth of the second cheek plate at least when the hinge mechanism is subjected to a torque that is greater than a predetermined value, the first cheek plate including at least one guide adapted under such circumstances to cooperate with a side bearing edge belonging to the jamming member and urging said jamming member by a wedging effect against the teeth of the second cheek plate;
the hinge mechanism has four jamming members, one of the jamming members being placed between the two locking slugs on one side of said diametral line and the other jamming members being placed on the other side of said diametral line, opposite the locking slugs;
the guides corresponding to said three other jamming members are formed by two portions in relief fixed relative to the first cheek plate, said two portions in relief also forming said two abutment zones; and
the cam is urged resiliently by a single spiral spring which is placed in a central housing formed in the first cheek plate, said spring extending between a first end connected to the first cheek plate and a second end connected to the cam.
The invention also provides a vehicle seat comprising a seat proper and a seat back interconnected by at least one hinge mechanism as defined above.